The ultimate goal of this proposal is to determine if exercise training an/or supplementation of the diet with amino acids can improve muscle strength and function in the elderly. Our focus will be on the promotion of net muscle protein synthesis, which is the metabolic basis for improved strength. We have previously shown that although healthy elderly individual have a decreased muscle mass, the ingestion of amino acids stimulates muscle protein synthesis to the same extent as in young individuals (1). In young individuals, muscle protein synthesis is also stimulated following resistance exercise (2). Further, when young individuals ingested amino acids after the exercise, the anabolic response to the amino acids was amplified (3). Our general hypothesis is that the same interactive effects between exercise and amino acid ingestion occur in the elderly. We propose that the basis for this interactive effect is that exercise increases the efficiency of the protein synthetic and amino acid transport processes. While the exogenous amino acids serve as precursors for synthesis and also minimize the increase in the rate of protein breakdown that normally occurs after exercise. Specifically, we will investigate the following hypotheses with regard to exercise, amino acids, and the elderly. 1. Specifically, we will investigate the following hypotheses with regarding to exercise, amino acids, and the elderly: 2. The stimulatory effect of ingestion of amino acids on muscle protein kinetics is amplified by prior exercise. 3. Exercise training diminishes the response of muscle protein synthesis to a single bout of exercise. Nonetheless, the ingestion of amino acids promotes met muscle protein synthesis to a greater extent in trained individuals after exercise than at rest. 4. The acute response to exercise and/or amino acid ingestion (i.e., over 2-3 hours) is reflected in corresponding changes in net muscle protein synthesis over 24 hours. Muscle protein kinetics will be determined using stable isotope tracer methodology and arterial-venous sampling acid and muscle biopsies. The results of these studies, coupled with the results of IDS#2, will lead to the design of an interventional study in which the long-term effects of exercise, hormonal therapy and/or nutrition will be assessed.